This invention generally relates to disk drives and other data storage devices. More particularly, this invention relates to disk drives having read/write channels with multiple input and output signals.
Disk drives are used as data storage components for computer systems and other electronic devices. Disk drives include computer hard disk drives, fixed disk drives, and the like. In general, disk drives have lower costs, higher storage capacities, higher reliability, lower power consumption, higher data transfer speed, and smaller physical size than other data storage devices.
A disk drive usually has one or more rotating magnetic disks encased within a housing. The disk drive includes various components for reading and writing data onto the magnetic disks and for interfacing with other devices. Typically, one or more read/write heads are positioned above the magnetic disks to read and write data. The read/write heads may be positioned on each side of a magnetic disk. The read/write head essentially forms the interface between a magnetic disk and the electronic components of the disk drive.
Each read/write head generates or senses electromagnetic fields or magnetic encodings on the magnetic disk as areas of magnetic flux. The presence or absence of flux reversals in the electromagnetic fields represents the data stored on the magnetic disk. A flux reversal is a change in the magnetic flux on contiguous areas of the magnetic disk. The presence or absence of magnetic flux reversals correspond to binary 1""s and 0""s of a diagnostic input signal. To xe2x80x9cwritexe2x80x9d data onto a magnetic disk, electronic components receive data from a host device and translate the data into magnetic encodings. The head transfers the magnetic encodings onto a portion of the magnetic disk. To xe2x80x9creadxe2x80x9d data from the magnetic disk, the head is positioned adjacent to the portion of the magnetic disk having the desired magnetic encodings. The head senses and transfers the magnetic encodings from the magnetic disk. The electronic components translate the magnetic encodings into the data, which is transferred to the host device. The host device may be a personal computer or other electronic equipment. The electronic components may apply error detection and correction algorithms to ensure accurate storage and retrieval of data from the magnetic disk. To improve data storage densities on disk drives, magneto resistive and inductive read/write heads have been developed with increased sensitivity to sense smaller amplitude magnetic signals and with increased signal discrimination.
Typically, a hard drive reads data by xe2x80x9cpeak detectionxe2x80x9dxe2x80x94detecting a voltage peak created when a flux reversal on a magnetic disk passes underneath the read/write head. However, a partial response maximum likelihood (PRML) algorithm has been developed to improve peak detection as densities and rotational speeds increase. PRML is implemented in the disk drive electronics to interpret the magnetic signals sensed by the read/write heads. PRML disk drives read the analog waveforms generated by the magnetic flux reversals stored on the disk. Rather than look for peak values to indicate flux reversals, PRML digitally samples the analog waveform (the xe2x80x9cpartial responsexe2x80x9d portion of the algorithm) and applies signal processing methodologies to determine the bit pattern represented by the waveform (the xe2x80x9cmaximum likelihoodxe2x80x9d portion of the algorithm).
The electric and mechanical components of the disk drive typically include a spindle motor, an actuator assembly, the read/write heads, amplifiers, a read/write channel, and a controller. There may be additional or different components having other configurations. The spindle motor holds and turns the magnetic disks. The actuator assembly positions the read/write heads adjacent to the magnetic disks. The amplifiers increase the signals between the read/write heads and the read/write channel. The controller interfaces between the read/write channel and the host device.
The read/write channel usually is implemented on an integrated circuit, which may be a complementary metal oxide semiconductor (CMOS). The read/write channel uses multiple input/out (I/O) terminals for inputting or outputting signals between the read/write channel and other components in the disk drive. Each read/write channel typically has four I/O terminalsxe2x80x94a write I/O terminal, a read I/O terminal, and two test or diagnostic I/O terminals. The write I/O terminal usually is used to output a write analog signal or voltage to the read/write heads. The write analog signal corresponds to the data to be stored on the magnetic disks. The read I/O terminal usually is used to input a read analog signal or voltage from the read/write heads. The read analog signal corresponds to the data stored on the magnetic disks. The diagnostic I/O terminals usually are used to input or output diagnostic or test signals such as an AC test bus output signal, a DC test bus input signal, and analog output signals from a diagnostic digital to analog converter. The read/write channel may have additional I/O terminals to expand or enhance the read and write operations of the disk drive and to perform additional diagnostic tests on the read/write channel.
Each I/O terminal usually has two pins for use with differential signals. With at least four I/O terminals, each read/write channel has at least eight pins. Each pin increases the cost and size of the integrated circuit or CMOS used to implement the read/write channel. Additionally, each pin increases the cost of using the integrated circuit or CMOS in the disk drive. Each pin usually has an external connection to other components in the hard drive. As the number of pins increases, the number of external connections increases.
This invention provides a read/write channel with a multiplex input/output system for a disk drive. The multiplex input/output system may send different signals or voltages through the same input/output terminal at essentially the same time or different periods of time.
A disk drive with a multiplex input/output system may have a read/write channel implemented on an integrated circuit. The disk drive may have a multiplex input/output (I/O) terminal, a write output driver, and a digital to analog converter. The multiplex input/output (I/O) terminal may be coupled one or more read/write heads. The write output driver may be coupled to provide a write output signal to the multiplex I/O terminal. A digital to analog converter may be coupled to provide an analog output voltage to the multiplex I/O terminal.
A read/write channel with a multiplex input/output system for a disk drive may have a multiplex input/output (I/O) terminal, a write output driver, a digital to analog converter, an analog to digital converter, and a test enable switch. The read/write channel may be implemented on an integrated circuit. The write output driver may be coupled to provide a write output signal to the multiplex I/O terminal. The digital to analog converter may be coupled to provide an analog output voltage to the multiplex I/O terminal. The analog to digital converter may be coupled to receive a diagnostic input voltage through the multiplex I/O terminal. The analog to digital converter may provide a diagnostic output signal in response to the diagnostic input voltage. The test enable switch may be coupled to the multiplex I/O terminal. The test enable switch may provide an output DC test signal to the multiplex I/O terminal. The test enable switch may receive an input DC test signal through the multiplex I/O terminal.
A read/write channel with a multiplex input/output system for a disk drive may have a first multiplex input/output (I/O) terminal, a write output driver, a digital to analog converter, an analog to digital converter (ADC), a test enable switch, a multiplex input/output (I/O) terminal, and a variable gain amplifier. The read/write channel may have partial response maximum likelihood (PRML) encoding and decoding and maybe implemented on a complementary metal oxide semiconductor. The write output driver may be coupled to provide a write output signal to the first multiplex I/O terminal. The digital to analog converter may be coupled to provide an analog output voltage to the first multiplex I/O terminal. The analog to digital converter may be coupled to receive a diagnostic input voltage through the first multiplex I/O terminal. The ADC may provide a diagnostic output signal in response to the diagnostic input voltage. The test enable switch may be coupled to the first multiplex I/O terminal. The test enable switch may provide an output DC test signal to the first multiplex I/O terminal. The test enable switch may receive an input DC test signal through the first multiplex I/O terminal. The variable gain amplifier may be coupled to receive a magnetically generated signal and an analog service signal through the second multiplex I/O converter. The write output signal, the analog output voltage, the diagnostic input voltage, and DC test signals are transmitted through the first multiplex I/O terminal at different times.
Other systems, methods, features, and advantages of the invention will be or will become apparent to one skilled in the art upon examination of the following figures and detailed description. All such additional systems, methods, features, and advantages are intended to be included within this description, within the scope of the invention, and protected by the accompanying claims.